The distance between a and B is 480km. Two cars a and B start from two places at the same time and run in opposite directions. They meet in six hours. It is known that the speed ratio of a and B is 9:7. What is the speed of a and B?

The distance between a and B is 480km. Two cars a and B start from two places at the same time and run in opposite directions. They meet in six hours. It is known that the speed ratio of a and B is 9:7. What is the speed of a and B?

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The sum of the speed of the two cars is per hour
480 △ 6 = 80 (km)
The speed of car a is per hour:
80 × 9 / (9 + 7) = 45 (km)
The speed of car B is per hour:
80 × 7 / (9 + 7) = 35 (km)
The speed sum of AB per hour is 480 △ 6 = 80 km
A speed: 80 ÷ (9 + 7) × 9 = 45 km / h
B speed: 80-45 = 35 km / h
Two vehicle speed sum = 480 △ 6 = 80 km / h
Vehicle a speed = 80 × 9 / 16 = 45 km / h
B vehicle speed = 80 × 7 / 16 = 35 km / h
A is 45 km / h, B is 35 km / h
Party A and Party B travel 480 / 6 = 80km in one hour
Then, the speed of a: 80 * 9 / (7 + 9) = 45km / h
Speed of B: 80 * 7 / (7 + 9) = 35km / h
A: 45 km / H B: 35 km / h
The speed ratio of the two vehicles is 3 to 5;
How many kilometers does car a travel per hour?
（1- 1/4）÷ 7/8 =6/7,
210 × 6 / 7 = 180km (speed and speed)
180 ÷ (3 + 5) × 3 = 67.5km/h (a speed)
Let the speed of car a be x and that of car B be y
x：y=3：5.
(x+y)*(7/8)=210*(1-1/4)
Sorting: x = 3Y / 5; 7 (3Y / 5 + y) = 1260, 21y + 35y = 6300, y = 6300 / 56 = 112.5 (km), x = 67.5 (km).
The speed of car a is 67.5km per hour, and that of car B is 112.5km per hour
The speed ratio of car a and car B is 4:5. How much does car a travel per hour
There are two cases
The two cars didn't meet, and they were still 1 / 4 of the distance,
Speed sum: 210x (1-1 / 4) △ 7 / 8 = 180 (km / h)
A + 1804 / km / h
After the two cars met, they were still 1-4 times away from each other,
Speed sum: 210x (1 + 1 / 4) △ 7 / 8 = 300 (km / h)
Car a per hour: 300x4 / (4 + 5) = 400 / 3 (km)
It is known that the quadratic equation of one variable X2 - (2k + 1) x + 4k-1 = 0 for X. if one side of isosceles ABC is a = 4, and the other two sides are exactly two solutions of this equation, the circumference of triangle can be obtained
Discriminant = (2k + 1) ^ 2-4 (4k-1) = 4K ^ 2 + 4K + 1-16k + 4 = 4K ^ 2-12k + 5 suppose a is the bottom, then the equation has two equal roots, discriminant = 04k ^ 2-12k + 5 = 0, k = 1 / 2 or 5 / 2 of the solution, substitute the two of K into the original x equation to find the root of X respectively, verify that the root of X is 1, 3 when x = 1, it can not form a triangle
A truck team carries a batch of goods, each truck is loaded with 4 tons, and there are still 8 tons left. Each truck is loaded with 4.5 tons, which is just finished
How many?
Set up x cars
equation
4x+8=4.5x
X=16
A bottle of 1 mineral water or two bottles of 5 jiao drink, which is more thirsty?
I think water is better. Drinks are not good for your health. I suggest you drink less,
The distance between a and B is 360 km, and the speed ratio of the bus and the truck is 5:3. How many kilometers does the truck travel per hour
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The bus and the truck go together every hour
360 △ 4.5 = 80 km
The bus runs every hour
80 × (5 + 3) 5 = 50 km
The truck runs every hour
80-50 = 30 km
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Speed sum = 360 △ 4.5 = 80 km / h
5+3=8
Bus speed = 5 / km / h = 80
Speed of truck = 80 × 3 / 8 = 30 km / h
The bus and the truck go together every hour
360 △ 4.5 = 80 km
The bus runs every hour
80 × (5 + 3) 5 = 50 km
The truck runs every hour
80-50 = 30 km
On the addition and subtraction of quadratic radical
I can't understand the main points of knowledge
If the result is a √ b... C √ B = (a... C) √ B
Some questions will be reversed
Just use it flexibly
The transportation team will rush 120 tons of disaster relief materials for the earthquake stricken area. If 8 trucks with a carrying capacity of 6 tons are used, the times of transportation and the quality of the disaster relief materials are as follows:
Times 1 2 3 4 5 6
Mass / T 20 40 60 80 100 120
What is the proportion between the number of times of transportation and the quality of the materials transported? Why?
A: it's a positive proportion, because the times of transportation and the materials transported are two related quantities, and their ratio (20) is fixed
In proportion
Because the quotient between the quality of times and the number of times of transportation is 20, it is in a positive proportion
Positive proportional relationship. Because the quality △ times = tonnage of each shipment (certain)
A: in proportion. Because the number of times of transportation and the quantity of materials transported are two related quantities, and the quantity changes with the number of times. Quantity: the number of times of transportation = the tonnage of each transportation (certain), which is 20. So it is in a positive proportion.
The price of Wahaha mineral water is 1.2 yuan per bottle. At present, a and B supermarkets offer preferential policies respectively, with 10% discount for all stores a and more than 20 bottles for stores B
20% off. If you are a consumer, which shopping mall is more suitable
If you buy x bottles of water, the total price of store a is Y1, and that of store B is Y2
y1＝1.2*0.9*x=1.08*x
y2=1.2x(x20)
When the price is the same, X / 200
When x28, B is better than a